Corrupt Root on new RAID

I've just got a new Netgear Ready NAS Duo, one with no supplied drives.

I've put a spare disk from my PC in. In case it's relevant it has historically been a boot drive but it's had a full format, not quick.

The PC is happy with the disk, but the RAIDar tool that comes with the NAS says 'corrupt root' as it's only words on the subject. I feel I must have done something stupid, but is there an easy way to fix this?

Managed to find a fix!

Because it was new I could do the hard factory reset, which would normally cost you all your data, but nothing to lose in this case.